A picture posted on Instagram by an actress less than half of Brad Pitt's age was yesterday alleged to be one of the key factors in the breakdown of his marriage to Angelina Jolie.

The image shows 24-year-old Selena Gomez gazing into Pitt's eyes at the Golden Globe awards earlier this year, and was said to have led Jolie to "blow a gasket".

Gomez, a former Disney child star, was said to have flirted with the actor throughout the evening and has spoken of her delight at meeting him. There is no suggestion that anything untoward happened between the pair.

Last night, there were growing signs that the so-called "Brangelina" divorce was descending in to bitter acrimony as Pitt's camp fought back against accusations that he was a philandering, drug-taking, poor parent.

Pitt (52) was said to be devastated by Jolie's decision to seek a divorce and is said to be furious at suggestions that she was concerned by his alleged alcohol consumption, marijuana smoking and "anger issues".

Jolie supposedly hired a private investigator to follow Pitt on set with Marion Cotillard, an actress to whom he was linked by the American media, during the filming of 'Allied' this spring. The French actress is expecting her second child with her boyfriend, the actor Guillaume Canet, and is said to be upset at being dragged into the divorce battle.

Mr Pitt has reportedly told friends not to speak ill of Ms Jolie, and praised her parenting skills. But her decision to demand sole custody, with Mr Pitt only given visitation rights, was unacceptable to the actor. Mr Pitt has told friends: "There's no chance that's going to happen," according to the gossip website TMZ. It reported that he said she had "unleashed hell" by allowing friends to discuss their relationship, and he was now concerned for the safety of the children.

The couple have three biological children - Shiloh, 10, and twins Knox and Vivienne, eight. They also have three adopted children - Maddox (15) from Cambodia; Pax (12) from Vietnam; and Zahara (11) from Ethiopia.

Jolie filed for divorce on Tuesday, citing irreconcilable differences. The couple were together for 12 years, marrying in 2014, and their divorce surprised even close friends, with George Clooney taken aback when asked about the separation during an American television interview.

Jolie was apparently angered by the photograph posted by Gomez (24) of her and Pitt at the Golden Globes awards, captioned: "Just discussing The Big Short." In 2013, Gomez told the chatshow host Ellen DeGeneres about her first meeting with Pitt, at the MTV awards that April. "They knocked on my door and they said Brad Pitt would like to come in and I was like, 'He can come in.' I was trying to play cool and be really nice. As soon as he walked out I ran and I hid under a table for like two minutes because I couldn't believe it was happening."

At the Golden Globes this year, Gomez had told reporters she was "on the look out" for Pitt and Ryan Gosling, who also starred in 'The Big Short'.

Brad Pitt and Angelina Jolie

A source told the 'National Enquirer': "Angie blew a gasket when she saw Selena's Instagram, and heard through friends about how Brad and Selena flirted so shamelessly."

Jolie guest-edited BBC Radio 4's 'Women's Hour' in June and spoke about her children's upbringing, detailing the diverse languages and range of skills boasted by her brood. "All the kids are learning different languages," she said.

"None of my kids want to be actors," she added. "They are actually very interested in being musicians."

The couple are said to have been arguing for some time and discussing divorce. But Pitt was only aware of her decision the day before his wife filed the documents. She "feels like a weight has been lifted," a source told gossip magazine 'US Weekly'. The actress's lawyer, Robert Offer, would only say: "This decision was made for the health of the family. She will not be commenting, and asks that the family be given its privacy at this time."

Jennifer Aniston (47), the actress whose marriage to Pitt ended after he and Jolie starred together in 'Mr and Mrs Smith', reportedly told friends "that's karma for you".